The present invention relates to the production of more uniform fabrics, and in particular, to the spreading of fibrous tows or zero-twist yarns used in producing woven and non-woven fabrics. In the fabric industry, particularly the reinforcing and structural fabric industry, rovings and zero twist yarns are used in weaving or stitching fabrics. Such fabrics then are used in many ways, including reinforcement of polymers or the creation of honeycomb reinforcements or supports.
Methods have long been sought to weave lighter weight webs of materials to reduce weight and cost. However, conventional production processes are limited in their ability to create lightweight webs of generally uniform areal weight. Several such processes disclosed in U.S. Pat. Nos. 4,556,440 and 4,667,831 dispose segments of a roving side by side to make a layer of material in a reinforcement fabric. However, the fabric varies randomly in areal weight along its length depending on how uniformly the fibers in the roving are spread across the weaving machine. Improvements which more uniformly spread the fibers of rovings used in fabrics would desirably reduce weight and cost, and more efficiently use the strength of the fibers. Such reinforcement fabrics are further used in the production of honeycomb materials which would similarly benefit from more uniformly spread fibers in the fabric layers which make up the honeycomb.
Fiber spreading processes are known in which rovings or zero twist yarns (both also referred to as tows) are resin impregnated and passed over a series of highly polished rolls to spread the width of the tow. Such methods for spreading fibers rely on the impregnant providing greater lubricity between fibers in the tow. Other methods of pneumatically opening fibrous tows are known in the art. However, the fibers so opened are only temporarily spread to permit the addition of a coating or other material, and are recombined into a tow.
Accordingly, the need exists to provide apparatuses and processes to more uniformly spread the fibers in a tow for use in existing apparatuses, processes and products.